Textile cord having an at least triple twist

ABSTRACT

A textile cord ( 50 ) with at least triple twist (T 1 , T 2 , T 3 ) comprises at least N strands ( 20   a,    20   b,    20   c,    20   d ), N being greater than 1, twisted together with a final twist T 3  and a final direction D 2 , each strand being made up of M pre-strands ( 10   a,    10   b,    10   c ), M being greater than 1, themselves twisted together with an intermediate twist T 2  (T 2   a , T 2   b , T 2   c , T 2   d ) and an intermediate direction D 1  opposite to D 2 , each pre-strand itself consisting of a yarn ( 5 ) which has been twisted on itself beforehand with an initial twist T 1  (T 1   a , T 1   b , T 1   c ) and the direction D 1 , in which at least half of the N times M yarns have an initial elastic modulus denoted Mi which is greater than 800 cN/tex. This textile cord can advantageously be used as a reinforcer in tires for vehicles, particularly in the belt or carcass reinforcement of these tires.

1. FIELD OF THE INVENTION

The present invention relates to the textile reinforcing elements or“reinforcers” that can be used to reinforce items made of plastic oritems made of rubber such as vehicle tyres.

It relates more particularly to textile cords or plied yarns that can beused notably for reinforcing such tyres.

2. STATE OF THE ART

Textiles have been used as reinforcers ever since tyres first appeared.

Textile cords, manufactured from continuous textile fibres such aspolyester, nylon, cellulose or aramid fibres, are known to play animportant part in tyres, even in high-performance tyres which have beenhomologated for running at very high speeds. In order to meet therequirements of the tyres, they need to have a high breaking strength, ahigh elastic modulus, good fatigue endurance and, finally, good adhesionto the rubber or other polymer matrices that they are liable toreinforce.

It will simply be recalled here that these textile plied yarns or cords,traditionally of the double twist (T1, T2) type, are prepared by amethod known as a twisting method, in which:

-   -   during a first step, each multifilament fibre or yarn that makes        up the final cord is first of all twisted individually on itself        (with an initial twist T1) in a given direction D1 (respectively        the S direction or the Z direction) to form a strand in which        the elementary filaments are deformed in a helix about the axis        of the fibre (or axis of the strand);    -   then, during a second step, several strands, generally two,        three or four, which are identical in nature or different in the        case of cords said to be hybrid or composite, are then twisted        together with a final twist T2 (which may be the same as or        different from T1) in the opposite direction D2 (respectively in        the Z direction or the S direction, according to a recognized        naming convention denoting the orientation of the turns        according to the cross bar of an S or of a Z) to obtain a cord        or final assembly comprising several strands.

The purpose of the twisting is to adapt the properties of the materialin order to create the transverse cohesion of the reinforcer, increaseits fatigue strength and also improve adhesion with the matrixreinforced.

Such textile cords, their constructions and methods of manufacture arewell known to those skilled in the art. They have been described indetail in a great many documents, for example in patent documents EP 021485, EP 220 642, EP 225 391, EP 335 588, EP 467 585, U.S. Pat. No.3,419,060, U.S. Pat. No. 3,977,172, U.S. Pat. No. 4,155,394, U.S. Pat.No. 5,558,144, WO97/06294 or EP 848 767, or more recently WO2012/104279,WO2012/146612, WO2014/057082, to name but a few.

In order to be able to reinforce rubber items such as tyres, the fatiguestrength (tensile, bending, compression endurance) of these textilecords is of key importance. It is known that, in general, for a givenmaterial, the greater the twist applied, the higher this fatiguestrength is, but that the counterpart to this is that the tensilebreaking force (referred to as tenacity when expressed per unit weight)of said textile cords decreases inexorably as the twist increases,something which of course is penalizing from the reinforcing viewpoint.

So, designers of textile cords, like tyre manufacturers, are constantlylooking for textile cords of which the mechanical properties,particularly breaking force and tenacity, for a given material and agiven twist, can be improved.

3. BRIEF DESCRIPTION OF THE INVENTION

Now, in the course of their research, the applicant companies havespecifically found a novel textile cord the specific architecture andconstruction of which unexpectedly, for a given material and a givenfinal twist, make it possible to improve the rupture force and tenacityproperties.

Thus, according to a first subject, the present invention relates to atextile cord with at least triple twist (T1, T2, T3) comprising at leastN strands, N being greater than 1, twisted together with a twist T3 anda direction D2, each strand being made up of M pre-strands, M beinggreater than 1, themselves twisted together with a twist T2 and adirection D1 opposite to D2, each pre-strand itself consisting of a yarnwhich has been twisted on itself beforehand with a twist T1 and thedirection D1, in which at least half of the N times M yarns have aninitial elastic modulus denoted Mi which is greater than 800 cN/tex.

The invention also relates to the use of such a textile cord as areinforcing element for items or semi-finished products made of plasticor of rubber such as pipes, belts, conveyor belts, vehicle tyres, and tothese items and semi-finished products made of rubber and tyresthemselves, both in the raw state (namely before curing or vulcanizing)and in the cured state (after curing).

The tyres of the invention, in particular, may be intended for motorvehicles of the passenger car, 4×4 or SUV (Sport Utility Vehicle) type,but may also be intended for two-wheeled vehicles such as motor bikes,or for industrial vehicles chosen from vans, heavy-duty vehicles i.e.metro trains, busses, road haulage vehicles (lorries, tractors,trailers) and off-road vehicles—agricultural or civil engineeringequipment, aircraft, other transport or handling vehicles.

The textile cord of the invention is quite particularly intended to beused in crown reinforcements (or belts) or in carcass reinforcements oftyres for the vehicles described hereinabove.

The invention and the advantages thereof will be readily appreciated inthe light of the detailed description and of the exemplary embodimentswhich follow, and of FIGS. 1 to 7 which relate to these embodiments andwhich (unless indicated otherwise without being drawn to a specificscale) depict:

-   -   in cross section, a conventional multifilament textile fibre (or        yarn) first of all in the initial state (5), namely without any        twist, and then after a first twisting operation T1 in the        direction D1 for formation of a yarn twisted on itself or        “pre-strand” (10) (FIG. 1);    -   in cross section, the assembly of 3 yarns (10 a, 10 b, 10 c) as        hereinabove, acting as pre-strands (twisted beforehand with T1        a, T1 b, T1 c in the same direction D1) which are assembled by a        second operation of twisting T2 still in the same direction D1,        for formation of a strand (20) intended for the cord according        to the invention (FIG. 2);    -   in cross section, the assembly of 3 strands (20 a, 20 b, 20 c)        as hereinabove (twisted beforehand with T2 a, T2 b, T2 c in the        same direction D1) which are assembled by a third operation of        twisting T3 this time in the direction D2 opposite to the        direction D1, for formation of a final textile cord (30) with        triple twist (T1, T2, T3) according to the invention (FIG. 3);    -   in cross section, the conventional assembly of 3 yarns (10 a, 10        b, 10 c) as hereinabove this time acting directly as strands        (all twisted beforehand with T1 a, T1 b, T1 c in the direction        D1) which are assembled by a second operation of twisting T2 in        the direction D2 which is opposite to the direction D1, for        formation of a textile cord according to the prior art (40) with        double twist (T1, T2) (FIG. 4);    -   in cross section, the assembly of 4 strands (20 a, 20 b, 20 c,        20 d) (twisted beforehand with T2 a, T2 b, T2 c, T2 d in the        same direction D1) which are assembled by a third operation of        twisting T3 in the direction D2 which is the opposite to the        direction D1, for formation of a final textile cord (50) with        triple twist (T1, T2, T3) according to the invention (FIG. 5);    -   in cross section, another depiction, less schematic than the        preceding one, of the above cord (50), illustrating the fact        that the final cross section of a textile cord (incidentally        whether or not it is a cord in accordance with the invention)        once formed and under minimal tension, is in fact more closely        similar to a cross section of circular outline, because of the        high degree of lateral plasticity afforded by the        multifilamentary nature of the starting material (FIG. 6);    -   finally, in radial section (which means to say in a plane        containing the axis of rotation of the tyre), an example of a        tyre according to the invention, incorporating a textile cord        according to the invention (FIG. 7).

4. DETAILED DESCRIPTION OF THE INVENTION

In the present application, unless expressly indicated otherwise, allthe percentages (%) indicated are mass percentages.

Any interval of values denoted by the expression “between a and b”represents the range of values extending from more than a to less than b(namely end points a and b excluded) whereas any interval of valuesdenoted by the expression “from a to b” means the range of valuesextending from a up to b (namely including the strict end points a andb).

The textile cord or plied yarn according to the invention is therefore(with reference to the appended FIGS. 1 to 3 and 5) a textile cord (30,50) of highly specific construction, which has the essential features ofcomprising:

-   -   at least a triple (which means to say three or more than three)        twist (T1, T2, T3);    -   at least N strands (20, 20 a, 20 b, 20 c, 20 d), N being greater        than 1, which are twisted together with a final twist T3 and a        same final direction D2;    -   each strand being made up of M pre-strands (10, 10 a, 10 b, 10        c), M being greater than 1, themselves twisted together with an        intermediate twist T2 (T2 a, T2 b, T2 c, T2 d) and an        intermediate direction D1 the opposite of D2;    -   each pre-strand consisting of a yarn (5) which has been twisted        on itself beforehand with an initial twist T1 (T1 a, T1 b, T1 c)        and the initial direction D1.

A person skilled in the art will immediately understand from theexpression cord having at least a triple twist (which means to sayhaving three twists or more) that at least three consecutive operationsof untwisting (or of twisting in the opposite direction) are thereforeneeded in order to “deconstruct” the cord of the invention and “getback” to the initial yarns of which it is made, namely to rediscover thestarting yarns (multifilament fibres) in their initial state, namelyfree of twist. Stated otherwise, there are at least three (three ormore) successive twisting operations to form the cord of the invention,rather than two as is usually the case.

Another essential feature is that at least half of the yarns that makeup the cord must have an initial elastic modulus Mi greater than 800cN/tex (thereby excluding notably nylon fibres), otherwise no increasein rupture force and tenacity is observed.

The structure of the textile cord of the invention and the stepsinvolved in manufacturing it will now be described in detail.

First of all, FIG. 1 schematically depicts in cross section aconventional multifilament textile fibre (5) also known as a “yarn”, inthe initial state, namely free of twist; as is well known, such a yarnis formed form a plurality of elementary filaments (50), typicallyseveral tens to several hundreds, of very fine diameter generally lessthan 25 μm.

After an operation of twisting T1 (first twist) in a direction D1 (S orZ), the initial yarn (5) is converted into a yarn twisted on itself andknown as a “pre-strand” (10). In this pre-strand, the elementaryfilaments thus find themselves deformed in a helix about the axis of thefibre (or the axis of the pre-strand).

Next, as illustrated by way of example in FIG. 2, M pre-strands (forexample here three of them; 10 a, 10 b, 10 c) are then themselvestwisted together, in the same direction D1 as before, with anintermediate twist T2 (second twist) to form a “strand” (20). Eachpre-strand is characterized by a specific first twist T1 (for examplehere, T1 a, T1 b, T1 c) which may be equal (in the general case, namelythat here for example, T1 a=T1 b=T1 c) or different from one pre-strandto another.

Finally, as schematically indicated in FIG. 3, N strands (for examplehere three strands; 20 a, 20 b, 20 c) are then themselves twistedtogether in the direction D2 which is opposite to D1, with a final twistT3 (third twist) to form the final textile cord (30) according to theinvention. Each strand is characterized by a specific second twist T2(for example here T2 a, T2 b, T2 c) which may be the same (in thegeneral case, namely here for example T2 a=T2 b=T2 c) or different fromone strand to another.

The final textile cord (30) thus obtained, comprising N times M (here,for example, nine) pre-strand, is therefore characterized by (at least)a triple twist (T1, T2, T3).

The invention of course applies to instances in which more than threesuccessive twists, for example four (T1, T2, T3, T4) or five (T1, T2,T3, T4, T5), are applied to the starting yarns (5). However, theinvention is preferably implemented with just three successiveoperations of twisting (T1, T2, T3), particularly for cost reasons.

FIG. 4, in comparison with FIG. 3, illustrates a conventional way ofpreparing double twist textile cords. M pre-strands (for example herethree strands, 10 a, 10 b, 10 c)—in fact directly acting as strands—aretwisted together, in a (second) direction D2 which is opposite to the(first) direction of twisting D1, to form directly a double twist (T1,T2) textile cord (40) according to the prior art.

FIG. 5 schematically depicts, in cross section, the assembly of 4strands (20 a, 20 b, 20 c, 20 d) (twisted beforehand with T2 a, T2 b, T2c, T2 d in the same direction D1) which are assembled by a thirdoperation of twisting T3 in the direction D2 which is opposite to thedirection D1, to form another example of final cord (50) with tripletwist (T1, T2, T3) according to the invention. Each strand ischaracterized by a specific second twist T2 (in this instance T2 a, T2b, T2 c, T2 d) which may be the same or different from one strand toanother.

As a reminder, FIG. 6 depicts, still in cross section, another depictionof the previous cord (50), less schematic than the preceding depiction,recalling the well-known fact that the cross section of a textile cord,incidentally whether or not it be one in accordance with the invention,once formed and under minimal tension, is in fact closer to acylindrical structure with a cross section of essentially circularoutline, because of the high degree of lateral radial plasticity of thestrands (20 a, 20 b, 20 c, 20 d) and pre-strands (10 a, 10 b, 10 c)afforded by the multifilamentary nature of the starting fibres (yarns).

In the present application, what is meant very generally by “textile” or“textile material” is any material made of a substance other than ametal, whether it be a natural substance or a synthetic substance, thatcan be converted into a thread, fibre or film by any suitable conversionmethod. Mention may be made, by way of nonlimiting example, of a polymerspinning method such as, for example, melt spinning, wet spinning or gelspinning.

Although materials made of a non-polymer material (for example a mineralsubstance such as glass or a non-polymer organic material such ascarbon) are included in the definition of a textile material, theinvention is preferably implemented using materials made of polymermaterial, either of the thermoplastic or of the non-thermoplastic type.

By way of examples of polymer materials, of thermoplastic or otherwisetype, mention may be made, for example, of celluloses, notably rayon,polyvinyl alcohols (PVA for short), polyketones, aramids (aromaticpolyamides), aromatic polyesters, polybenzazoles (PBO for short),polyimides, polyesters, notably those chosen from PET (polyethyleneterephthalate), PEN (polyethylene naphthalate), PBT (polybutyleneterephthalate), PBN (polybutylene naphthalate), PPT (polypropyleneterephthalate), PPN (polypropylene naphthalate).

Of course, the invention applies to instances in which the textile cordof the invention is formed of several yarns of different materials toconstitute a hybrid or composite yarn, for example based on yarns of atleast polyester and nylon, or polyester and cellulose, or polyester andpolyketone, or polyketone and nylon, or cellulose and nylon, orcellulose and polyketone, or cellulose and aramid, or aramid and nylon,or aramid and polyester (for example PET or PEN), or even aramid andpolyketone, to name but a few examples, at least half of the N times Myarns of course having a modulus Mi greater than 800 cN/tex.

In the cord of the invention, N preferably varies in a range from 2 to6, more preferably from 2 to 4. According to another preferredembodiment, M varies in a range from to 2 to 6, more preferably from 2to 4. According to another preferred embodiment, the total number ofyarns (equal to N times M) is comprised in a range from 4 to 25, morepreferably from 4 to 16.

In a way well known to those skilled in the art, the twists may bemeasured and expressed in two different ways, namely, and in a simpleway, as number of turns per metre (t/m) or, and more rigorously whenwishing to compare materials of different natures (cubic densities)and/or different yarn counts, in terms of the twist angle of thefilaments or, which is equivalent, in the form of a twist factor K.

The twist factor K is connected to the twist T (here, for example, toT1, T2 and T3 respectively) by the known relationship as follows:

K=(twist T)×[(yarn count/(1000·φ]^(1/2)

in which the twist T of the elementary filaments (that make up thepre-strand, strand or plied yarn) is expressed in turns per metre (t/m),the yarn count is expressed in tex (weight in grams of 1000 metres ofpre-strand, strand ρ or plied yarn) and finally p is the density orcubic density (in g/cm³) of the material of which the pre-strand, strandor plied yarn is made (for example, around 1.50 g/cm³ for cellulose,1.44 g/cm³ for aramid, 1.38 g/cm³ for a polyester such as PET, 1.14g/cm³ for nylon); in the case of a hybrid cord, ρ is of course anaverage of the densities weighted by the respective yarn counts of thematerials that make up the pre-strands, strands or plied yarns.

In the cord of the invention, for preference, the twist T1 expressed inturns per metre (t/m) is comprised between 10 and 350, more preferablybetween 20 and 200. According to another preferred embodiment, eachpre-strand has a twist coefficient K1 which is comprised between 2 and80, more preferably between 6 and 70.

According to another preferred embodiment, the twist T2 expressed inturns per metre is preferably comprised between 25 and 470, morepreferably between 35 and 400. According to another preferredembodiment, each strand has a twist coefficient K2 which is comprisedbetween 10 and 150, more preferably between 20 and 130.

According to another preferred embodiment, the twist T3 expressed inturns per metre is preferably comprised between 30 and 600, morepreferably between 80 and 500. According to another preferredembodiment, the cord of the invention has a twist coefficient K3 whichis comprised between 50 and 500, more preferably between 80 and 230.

For preference, T2 is greater than T1 (T1 and T2 notably being expressedin t/m). According to another preferred embodiment, which may or may notbe combined with the previous one, T2 is less than T3 (T2 and T3 beingnotably expressed in t/m), T2 being more preferably comprised between0.2 and 0.95 times T3, in particular between 0.4 and 0.8 times T3.

According to another preferred embodiment, the sum T1+T2 is comprisedbetween 0.8 and 1.2 times T3, more preferably between 0.9 and 1.1 timesT3 (T1, T2 and T3 being notably expressed in t/m), T1+T2 in particularbeing equal to T3.

In the cord of the invention, for preference the majority (by number),more preferably all of the N times M yarns (in the initial state, namelywithout the twist T1) have a modulus Mi which is greater than 800cN/tex, notably than 1000 cN/tex. The initial elastic modulus Mi, orYoung's modulus, is of course the longitudinal elastic modulus, namelythe one along the axis of the yarn.

More preferably still, at least half, particularly most (by number) ofthe N times M yarns have a modulus Mi greater than 1200 cN/tex, moreparticularly greater than 1400 cN/tex. More preferably still, it is allof the N times M yarns that have a modulus Mi greater than 1000 cN/tex,notably greater than 1200 cN/tex, more particularly greater than 1400cN/tex.

All the properties (yarn count, initial modulus of the yarns, breakingstrength and tenacity) indicated hereinabove are determined at 20° C. onbare (which means to say uncoated) cords or on coated cords (which meansto say cords that are ready for use or have been extracted from the itemthat they reinforce) which have been subjected to a prior conditioning;what is meant by “prior conditioning” is that the cords (after drying)are stored for at least 24 hours, prior to measurement, in a standardatmosphere in accordance with European Standard DIN EN 20139(temperature of 20±2° C.; relative humidity of 65±2%).

The yarn count (or linear density) of the pre-strands, strands or cordsis determined on at least three specimens, each corresponding to alength of at least 5 m by weighing of this length; the yarn count isgiven in tex (weight in grams of 1000 m of product—remember: 0.111 texis equal to 1 denier).

The tensile mechanical properties (tenacity, initial modulus, elongationat break) are measured in a known way using an INSTRON tensile testmachine fitted with capstan grips of the “4D” type (for breakingstrengths of below 100 daN) or “4E” type (for breaking strengths atleast equal to 100 daN), unless indicated otherwise according toStandard ASTM D885 (2010). The tested specimens are subjected totraction over an initial length of 400 mm in the case of the 4D gripsand 800 mm in the case of the 4E grips, at a nominal rate of 200 mm/min,under a standard pretension of 0.5 cN/tex. All the results given are amean over 10 measurements. When the properties are measured on yarns,these, in the well-known way, undergo a very light prior twist referredto as “protective twist”, corresponding to a twist angle of about 6degrees, before they are positioned and tensioned in the grips.

The tenacity (breaking strength divided by yarn count) and initialelastic modulus (or Young's modulus) are given in cN/tex or centinewtonper tex (remember: 1 cN/tex is equal to 0.111 g/den (gram per denier)).The initial modulus is represented by the tangent at the origin of theforce-elongation curve, described as the gradient of the linear part ofthe force-elongation curve that occurs just after a standard pretensionof 0.5 cN/tex. The elongation at break is indicated as a percentage.

5. EXEMPLARY EMBODIMENTS OF THE INVENTION

The textile cord o the invention can advantageously be used to reinforcetyres of all types of vehicles, particularly motor bikes, passengervehicles, or industrial vehicles such as heavy duty vehicles,construction plant vehicles, aircraft, other transport or handlingvehicles.

By way of example, FIG. 7 very schematically (and not to scale) depictsa radial cross section through a tyre according to the invention, forexample for a vehicle of the passenger vehicle type.

This tyre 100 comprises a crown 102 reinforced by a crown reinforcementor belt 106, two sidewalls 103, and two beads 104, each of these beadsbeing reinforced with a bead wire 105. The crown 102 is surmounted by atread, not depicted in this schematic figure. A carcass reinforcement107 is wrapped around the two bead wires in each bead, the turnup 108 ofthis reinforcement 107 for example being positioned towards the outsideof the tyre 100 which here is depicted mounted on its rim 109.

In a way known per se the carcass reinforcement 107 is made up of atleast one rubber ply reinforced with what are known as “radial” textilecords, which means to say that these cords are arranged practicallyparallel to one another and extend from one bead to the other in such away as to form an angle comprised between 80° and 90° with thecircumferential mid plane (plane perpendicular to the axis of rotationof the tyre which is situated midway between the two beads 104 andpasses through the middle of the crown reinforcement 106).

The belt 106 is made up for example, in a way known per se, of at leasttwo rubber plies referred to as “working plies” or “triangulation plies”which are superposed and crossed, reinforced with metal cords arrangedsubstantially parallel to one another and inclined with respect to thecircumferential mid plane, it being possible for these working plies tobe associated or not with other rubber plies and/or fabrics. Theseworking plies have the prime function of giving the tyre casing highcornering stiffness. The belt 106 further comprises in this example arubber ply referred to as a “hooping ply” which is reinforced withreinforcing threads referred to as “circumferential” which means to saythat these reinforcing threads are arranged practically parallel to oneanother and run substantially circumferentially around the tyre casingso as to form an angle preferably comprised in a range from 0 to 10°with the circumferential mid plane. These circumferential reinforcingthreads have the prime function, it will be recalled, of resisting crownspin-out at high speed.

This tyre 100 of the invention has, for example, the essential featurethat at least the hooping ply of its belt (106) and/or its carcassreinforcement (107) comprises a textile cord according to the invention.According to another possible exemplary embodiment of the invention, itis for example the bead wires (105) which may be made, in full or inpart, of a textile cord according to the invention.

The rubber compositions used for these plies are compositions that areconventional for the skimming of textile reinforcers, typically based onnatural rubber or some other diene elastomer, on a reinforcing fillersuch as carbon black, on a vulcanizing system and the usual additives.Adhesion between the composite textile cord of the invention and thelayer of rubber with which it is coated is afforded for example by ausual adhesive composition, for example an adhesive of RFL type orequivalent adhesive.

Because of its specific construction, the textile cord of the inventionhas notably improved tensile test properties, as demonstrated by thefollowing exemplary embodiments.

In these exemplary embodiments, 6 different tensile tests were conductedfirst of all with the manufacture, in total, of 13 different textilecords, based on nylon, rayon or aramid, in accordance or not inaccordance with the invention.

The nature of each example of cord (“T” for the control, “C” forcomparative and “I” for those in accordance with the invention), thematerial used (“N” for nylon, “R” for rayon, “A” for aramid), itsconstruction and final properties are summarized in the attached table1.

The starting yarns are of course commercially available, for example inthe case of nylon sold by the company Kordsa under the name “T728” or bythe company PHP under the names “Enka 140HRT” or “Enka 444HRST”, in thecase of rayon by the Cordenka company under the name of “C610-F Super2”,in the case of aramid by the Teijin company under the name of “Twaron1000”.

As already indicated, the tenacity is the force at break with respect tothe yarn count and is expressed in cN/tex. Also indicated is theapparent tenacity (in daN/mm²), and in this case the force at break isrelated to the apparent diameter denoted Ø which is measured inaccordance with the method as follows.

Use is made of an apparatus which, using a receiver made up of anoptical collector system, of a photodiode and of an amplifier, makes itpossible to measure the shadow of a thread illuminated by a laser beamof parallel light with a precision of 0.1 micrometre. Such an apparatusis marketed for example by the company Z-Mike under the reference“1210”. The method involves fixing to a motorized mobile table, under astandard preload of 0.5 cN/tex, a specimen of the thread that is to bemeasured, which has undergone conditioning beforehand. Secured to themobile table, the thread is moved perpendicular to the cast-shadowmeasurement system at a speed of 25 mm/s and intersects the laser beamorthogonally. At least 200 cast-shadow measurements are taken over a 420mm length of thread; the mean of these cast-shadow measurementsrepresents the apparent dimeter Ø.

For each test, the breaking force, tenacity and apparent tenacity havealso been indicated in terms of relative values, base 100 being used forthe control cord in each test.

The control cords (denoted “T” in table 1) are all characterized by aconventional double twist T1, T2 construction; the other cords(comparative or in accordance with the invention) are all characterizedby an unconventional triple twist T1, T2, T3 construction. However, onlythe cords according to the invention combine the triple twist featurewith an initial yarn modulus greater than 800 cN/tex.

To make this table 1 easier to read, it will be noted here that, forexample, the construction denoted “N47/-/3/4” for control cord C1 meansthat this cord is a double twist (T1, T2) cord which is derived simplyfrom an operation of twisting (T2, D2 or S) 4 different strands whichhave each been prepared beforehand by an operation of individuallytwisting 3 nylon (N) yarns with a yarn count of 47 tex in the oppositedirection (T1, D1 or Z).

By way of comparison, for the construction denoted “N47/1/3/4” (cordC2), the textile cord in question is a triple twist (T1, T2, T3) cordwhich is derived from an operation of final twisting (T3, D2 or S) of 4different strands which have each been prepared beforehand by anoperation of intermediate twisting (T2) of 3 pre-strands in the oppositedirection (D1 or Z), each of the pre-strands consisting of a singlenylon (N) yarn of yarn count 47 tex which has been twisted on itselfbeforehand during a first operation of twisting T1 in the same directionD1 (Z).

The 6 examples of control cords (denoted “T”) C1, C3, C5, C7, C9 and C12are all characterized by a double twist construction; they have beenmanufactured by assembling 2, 3 or 4 strands with a (second) final twist(denoted T2) from 150 to 300 t/m, corresponding to a twist coefficientK2 varying from 175 to 215, and a direction D2 (S direction). In theconventional way, each of these strands had been manufactured beforehandwith a (first) initial twisting (denoted T1) from 150 to 300 t/m as thecase may be of a yarn on itself in the opposite direction D1 (Zdirection).

The 4 examples of cords according to the invention (denoted “I” and inbold in table 1) C8, C10, C11 and C13 are all characterized by a tripletwist T1, T2, T3 construction (in these examples, Z/Z/S); they weremanufactured by assembling 3 or 4 strands with a final twist (denotedT3) of 150 to 300 t/m, corresponding to a twist coefficient K3 varyingfrom 180 to 215, and a direction D2 (S direction). According to theinvention, each of these strands had been manufactured beforehand byassembly of 3 pre-strands with a twist T2 (110 to 240 t/m as the casemay be) and an opposite direction D1 (Z direction), each of thesepre-strands having itself been prepared beforehand by a twisting T1 (40to 120 t/m as the case may be) of a yarn on itself in the direction D1(Z direction).

As for the 3 comparative examples of cords not in accordance with theinvention (denoted “C”) C2, C4 and C6, these are all characterized by atriple twist T1, T2, T3 construction. They were prepared rigorously likethe cords according to the invention, the only difference being in thefact that the yarns that make up these cords, all made of nylon, had aninitial modulus Mi markedly lower than 800 cN/tex.

From studying this table 1 in detail it is first of all noted, for tests1 to 3, all conducted with nylon yarns (initial modules of 440 cN/texapproximately), that switching from the double twist (C1, C3 and C5) tothe triple twist (C2, C4 and C6) is not accompanied by any appreciablechange to the breaking strength or to the other properties (Ø and yarncount).

By contrast, for tests 4 to 6, conducted with yarns of which the initialmodulus Mi is greater than 800 cN/tex, more specifically with rayonyarns (Mi of around 1000 cN/tex) or aramid yarns (Mi of around 4000cN/tex) it is possible to see that switching from the double twistconstruction (C7, C9 and C12) to the triple twist construction (C8, C10,C11 and C13), is unexpectedly accompanied, with all other parametersremaining unchanged, by:

-   -   an improvement of at least 5% in the breaking strength,        something which is quite significant to a person skilled in the        art;    -   combined with an appreciable reduction in the apparent diameter        Ø and yarn count, these being clear indicators of better        compactness of the cord according to the invention and        ultimately of the quality of the reinforcer, because of its        highly specific construction;    -   all of this ultimately resulting in an increase of more than 10%        in the apparent tenacity;    -   it being possible for the increases in breaking strength and        apparent tenacity to even exceed 15% and 25%, respectively, in        the case of cord C13 according to the invention.

The tests mentioned above were supplemented by an additional test (test7 in table 1) conducted on two more different textile cords C14(control) and C15 (invention), this time based on polyester (P), of thePEN type (“A701” by the Honeywell company; a yarn with a yarn count of110 tex, having an initial elastic modulus of around 1700 cN/tex).

In a way similar to the constructions commented upon hereinabove, theconstruction denoted “P110/-/3/2” for control cord C14 means that thiscord is a double twist (T1, T2) cord derived simply from an operation oftwisting (T2 of 260 t/m, D2 or S) of 2 different strands each of whichwas prepared previously by an operation of individual twisting (T1 of260 t/m, D1 or Z) of 3 polyester (P) yarns of 110 tex yarn count in theopposite direction.

Comparatively, for the construction denoted “P110/1/3/2” of the cord C15according to the invention, the textile cord concerned is a triple twist(T1, T2, T3) cord derived from an operation of final twisting (T3 of 260t/m, D2 or S) of 2 different strands which have each been preparedbeforehand by an operation of intermediate twisting (T2 of 155 t/m) inthe opposite direction (D1 or Z) of 3 pre-strands, each of thepre-strands consisting of 1 single polyester (P) yarn of 110 tex yarncount which was twisted on itself beforehand during a first operation oftwisting T1 (105 t/m) in the same direction D1 (Z).

The results obtained have been added to table 1. They confirm thesuperiority of the cord C15 of the invention, as compared with thecontrol cord C14 with an increase of nearly 5% for breaking strength andof 10% for apparent tenacity, accompanied by a decrease in the apparentdiameter and in the yarn count.

In conclusion, by virtue of the invention it is now possible, for agiven material and a given final twist, to improve the properties ofcompactness, breaking strength and tenacity of the textile cords thatcan be used to reinforce tyres, and thus further optimize thearchitecture of said tyres.

TABLE 1 Initial Modules Twist Mechanical properties of the Twist t/mCoefficient Breaking ø Yarn Apparent Test Cord Cord Cord Yarn — T1 T2 —K1 K2 strength apparent count Tenacity tenacity No. ref. typeConstruction cN/tex T1 T2 T3 K1 K2 K3 daN mm tex cN/tex daN/mm² 1 C1 TN47/-/3/4 440 0 250Z 250S 0 88 176 35.3 100 1.05 638 55 100 41 100 C2 CN47/1/3/4 440 100Z 150Z 250S 20 53 176 34.1 97 1.02 642 53 96 42 102 2C3 T N94/-/2/3 440 0 260Z 260S 0 106 183 41.2 100 1.03 636 65 100 50 100C4 C N94/1/2/3 440 100Z 160Z 260S 29 65 183 42.3 103 1.04 640 66 102 50100 3 C5 T N140/-/2/2 440 0 250Z 250S 0 124 175 44.5 100 1.02 613 73 10054 100 C6 C N140/1/2/2 440 100Z 150Z 250S 35 74 175 43.5 98 1.03 608 7299 52 96 4 C7 T R122/-/3/4 1000 0 180Z 180S 0 90 180 46.5 100 1.56 173027 100 24 100 C8 I R122/1/3/4 1000 40Z 140Z 180S 12 70 180 48.7 105 1.521719 28 105 27 113 5 C9 T A55/-/3/4 4000 0 300Z 300S 0 102 203 110.6 1001.07 777 142 100 122 100 C10 I A55/1/3/4 4000 60Z 240Z 300S 12 81 203119.4 108 1.03 764 156 110 143 117 C11 I A55/1/3/4 4000 120Z 180Z 300S23 61 203 116.9 106 1.04 765 153 108 137 112 6 C12 T A330/-/3/3 4000 0150Z 150S 0 124 215 404.2 100 2.48 3482 116 100 84 100 C13 I A330/1/3/34000 40Z 110Z 150S 19 91 215 467.8 116 2.37 3428 136 117 106 126 7 C14 TP110/-/3/2 1700 0 260Z 260S 0 128 181 43.3 100 1.08 749 58 100 47 100C15 I P110/1/3/2 1700 105Z 155Z 260S 30 76 181 44.9 104 1.06 743 60 10451 108

1.-22. (canceled)
 23. A textile cord with at least triple twistcomprising: at least N strands, N being greater than 1, twisted togetherwith a twist T3 and a direction D2, wherein each strand is made up of Mpre-strands, M being greater than 1, themselves twisted together with atwist T2 and a direction D1 opposite to D2, wherein each pre-strandconsists of a yarn which has been twisted on itself with a twist T1 andthe direction D1, and wherein at least half of the N times M yarns havean initial elastic modulus denoted Mi which is greater than 800 cN/tex.24. The textile cord according to claim 23, wherein N varies in a rangefrom 2 to
 6. 25. The textile cord according to claim 24, wherein Nvaries in a range from 2 to
 4. 26. The textile cord according to claim23, wherein M varies in a range from 2 to
 6. 27. The textile cordaccording to claim 26, wherein M varies in a range from 2 to
 4. 28. Thetextile cord according to claim 23, wherein the total number N times Mof yarns is comprised in a range from 4 to
 25. 29. The textile cordaccording to claim 28, wherein the total number N times M of yarns iscomprised in a range from 4 to
 16. 30. The textile cord according toclaim 23, wherein the twist T1, expressed in turns per meter, comprisesbetween 10 and 350 turns per meter.
 31. The textile cord according toclaim 30, wherein the twist T1 comprises between 20 and 200 turns permeter.
 32. The textile cord according to claim 23, wherein eachpre-strand has a twist coefficient K1 which comprises between 2 and 80.33. The textile cord according to claim 32, wherein each pre-strand hasa twist coefficient K1 which comprises between 6 and
 70. 34. The textilecord according to claim 23, wherein the twist T2, expressed in turns permeter, comprises between 25 and 470 turns per meter.
 35. The textilecord according to claim 34, wherein the twist T2 comprises between 35and 400 turns per meter.
 36. The textile cord according to claim 23,wherein each strand has a twist coefficient K2 which comprises between10 and
 150. 37. The textile cord according to claim 36, wherein eachstrand has a twist coefficient K2 which comprises between 20 and 130.38. The textile cord according to claim 23, wherein the twist T3,expressed in turns per meter, comprises between 30 and 600 turns permeter.
 39. The textile cord according to claim 38, wherein the twist T3comprises between 80 and 500 turns per meter.
 40. The textile cordaccording to claim 23, wherein the cord has a twist coefficient K3 whichcomprises between 50 and
 500. 41. The textile cord according to claim40, wherein the cord has a twist coefficient K3 which comprises between80 and
 230. 42. The textile cord according to claim 23, wherein T2 isgreater than T1.
 43. The textile cord according to claim 23, wherein T3is greater than T2.
 44. The textile cord according to claim 43, whereinT2 comprises between 0.2 and 0.95 times T3.
 45. The textile cordaccording to claim 44, wherein T2 comprises between 0.4 and 0.8 timesT3.
 46. The textile cord according to claim 23, wherein the sum T1+T2comprises between 0.8 and 1.2 times T3.
 47. The textile cord accordingto claim 46, wherein the sum of T1+T2 comprises between 0.9 and 1.1times T3.
 48. The textile cord according to claim 46, wherein the sumT1+T2 is equal to T3.
 49. The textile cord according to claim 23,wherein all of the N times M yarns have a modulus Mi greater than 800cN/tex.
 50. The textile cord according to claim 23, wherein at leasthalf of the N times M yarns have a modulus Mi greater than 1000 cN/tex.51. The textile cord according to claim 50, wherein all of the N times Myarns have a modulus Mi greater than 1000 cN/tex.
 52. The textile cordaccording to claim 51, wherein all of the N times M yarns have a modulusM greater than 1200 cN/tex.
 53. A method of reinforcing an item orsemi-finished product made of plastic or of rubber comprising the stepof including a textile cord according to claim 23 in the item orsemi-finished product.
 54. An item or semi-finished product made ofplastic or of rubber reinforced with a textile cord according to claim23.
 55. A method of reinforcing a tire comprising the step of includinga textile cord according to claim 23 in a tire.
 56. A tire reinforcedwith a textile cord according to claim 23.